Construction of bridges.



No. 713,684. Patented Nov. I8,l902.

H. PRINZHORN.

CONSTRUCTION UF BRIDGES.

QAppumion me@ .my so, 190x.)

(No Model.)

l fw ITam/EW.

ma Nonrus PETERS co, Pnommwo., wAsmNmoN. n. u,

llni'rnn @trarne Parnu'r FFICE@ CONSTRUCTION OF BRIDGES.

SPECIFICATION forming part of Letters Patent No. 713,684, dated November 18, 1902.

Application tiled July 30, 1901. Serial No. 70,262. (No model.)

To all whom t may concern:

Be it known that I, HERMANN PRINZHORN, a subject of the King of Prussia, Emperor ot' Germany, residing at Halle-on-the-Saale, Germany, have invented certain new and useful Improvements in the Construction of Bridges; and I do hereby declare the following to be a full, clear, and exact description of the same.

By the coordination of the cantaliver and the suspension systems it is possible to bridge over large spans at comparatively light expense. There are only two kinds of systems known up to the present time adapted to this purpose-namely, the suspension-bridge, in connection with stiffening-trusses, and the cantaliver system. Either of these systems, however, must be abandoned on account ot' the immense cost of construction as soon as the width of span surpasses a certain measure-say about two thousand feet-if at the same time a heavy moving` load is expected to be carried over the bridge.

Now the leading idea of my invention is to combine the advantages of both systems in such a manner that instead of the stitfeningtruss, which has to be connected With every suspension-bridge, a cantaliver-truss is introduced, requiring, as the case may be, more or less the amount of material of the stiifening-truss, but in this new shape representing a truss of great carrying strength and one which at the same time is adapted to resist the force of wind and lateral motions, as well as greatly relieving the cable. This latter object is not nearly as well attained by the stiffening -truss of suspension bridges, because in order to overcome the lateral forces it has to be of great stitfness-that is to say, heavily constructed-and consequently increasing the cross-section of the cable without its taking much part in the support ot' the loads.

Now the principle to be embodied by my invention is to distribute the load to be carried bythe cantaliver in such a manner that the load is comparatively small near the center of the span and comparatively large near the towers,while the cable-load is distributed eorrespondingly--that is to say, in the opposite manner. By this arrangement the 1no ments of the load resisted by the chords of the truss will not exceed reasonable limits even in large spans.

In order to obtain and maintain the specific distribution of the load carried by the cantaliver under any moving load and at any temperature, not only must the lengths of the Suspenders s be such that the curve of the suspended cable is in correspondence with the distribution of the load carried by the latter, but a second condition is that there must be free and unembarrassed longitudinal eX- tension or contraction of the truss caused by changing temperatures. For this latter purpose the ends of both trusses meeting in the middle of the span are provided with mutual supports, allowing either truss to expand freely, but preventing any individual lateral or vertical motion of the meeting ends--that is to say, forcing either truss to follow the movement of the other in every direction except the longitudinal direction.

By the constructions shown in the drawings or similar connections the ends ofthe trusses meeting in the center of span are prevented from being disconnected if one truss is fully loaded, while the other is only carrying its permanent load, in which case the former truss is supported by the latter. A close fit of the bearings is desirable and may be obtained without practical diiculty.

In Athe accompanying drawings, Figure l shows a part of my improved bridge in side elevation. Fig. 2 is a plan view. Fig. 3 shows in enlarged sectional plan a form of sliding connection between adjacent ends of the cantalivers. Fig. 3 is a section at right angles to that of Fig. 3. Fig. 4: is an enlarged vertical section through the pressure-head, and Fig. 5 is a sectional plan.

The trusses A B rest on the pillars C, which also carry the iron towers E, supporting the cables K. The ends of the truss-girder A, meeting in the center of the bridge or span, are connected with each other in such a manner that either may move independently in longitudinal, but not in vertical or lateral, direction. For this purpose one truss may be provided with pins F, sliding in suitable bearings G ot' the other truss, Figs. 3 and The sliding connections might, however, as well be otherwise constructed.

IOO

I make use of the lateral girder or truss B as an abutment for the cable. By this arrangement the whole retaining construction, including the heavy and costly masonry of the retaining-abutments, may be dispensed with, while the rising and falling of the cable in the center of the bridge, caused by variations of temperature, is also considerably reduced, as the side girder moving in the same direction absorbs the extension of the cable in the lateral span. This diminution of the rising and falling of the cable has also a favorable eiect in regard to the vadoption of the limits of strains, allowing under equal circumstances the use of smaller cross-sections than in case of retaining-cables.

To retain the cable, either chord of the lateral truss B may be suitable; but in most cases the lower chord has to be given the preference. At any rate the chord chosen for this purpose has to be provided with a head of cast steel or iron fitted to the purpose, as, for instance, shown at 7c in the drawings. The cable may either be divided into strings running around the end of chord or be fastened to the above-mentioned head in other suitable fashion.

In the case illustrated in Figs. 4 and 5 the ends of the lower chords are provided with pressure-heads 7c, around which passes the cable K, divided into separated strands.

' I claim as my invention- I. In a bridge, the combination of suspension-cables and cantaliver-trusses, towers and piers, and Suspenders connecting the cables and trusses, the towers being securely anchored to their piers, with the cables anchored rmly on the land side of the piers, and a lateral bearing between the central trusses, all substantially as described.

2. In a bridge, the-combination of suspension-cables and two towers anchored iirmly at their bases, with cantaliver-trusses secured to the towers and extending one on either side thereof, the cables being anchored securely to the end of the shore-trusses, suspenders connecting the cables and trusses and a lateral bearing for the central trusses, substantially as described.

In testimony whereof I have signed my name to this specification in the presenceof two subscribing witnesses.

' HERMANN PRINZHORN.

Witnesses:

CARL GUsTAv GNZEL, RUDOLPH FRICKE. 

